When a certain no 'x' is multiplied by 18,the product 'y' has all digits as 4s. What is the minimum no of digits'x' can have?
a)8 b)9 c)12 d)18

• Ans (a)8
  18x=y
  x=y/18
  18=9*2
  according to the divisibility rule of 2 and 9
  y is divisible by 2
  for being divisible by 9 sum of all digits should be divisible by 9
  so 9 times 4 = 36 is divisible by 9 (minimum sum)
  18x=444444444
  x=444444444/18
  x= 8 digit no.
  
• 10 years agoHelpfull: Yes(47) No(11)
• a/q -18*x=y ,which contain all 4
  then y should be divisible by 18 completely ,to get integer value of x
  or ,it should be divisible by 9 and 2 completely
  now a no will only be divisible by 9 if sum of the no is divisible by 9
  so, clearly it wl be 9(9times4=36)
• 10 years agoHelpfull: Yes(18) No(6)
• question is
  18x=y where in y all digits are 4
  so we can say
  9x=y where in y all digits are 2
  so,
  x=y/9
  here x is an integer so y should be divisible by 9
  and divisibility rule for 9 is sum of all digit will be divisible by 9
  and y containing only 2 so 9 digit make the sum 18 which is divisible by 9
  so number of digit will be 9
• 10 years agoHelpfull: Yes(5) No(1)
• question is
  18x=y where in y all digits are 4
  so we can say
  9x=y where in y all digits are 2
  so,
  x=y/9
  here x is an integer so y should be divisible by 9
  and divisibility rule for 9 is sum of all digit will be divisible by 9
  and y containing only 2 so 9 digit make the sum 18 which is divisible by 9
  so number of digit will be 9
• 10 years agoHelpfull: Yes(3) No(6)
• 18x=y
  so x=y/18, for minimum value of x, so y must have minimum value which is divisible by 18
  now y/18 gives 246958
  so x has 6 digits.
  
  note- in the question we have to find the no digits of x not y.
• 10 years agoHelpfull: Yes(2) No(0)
• 9 ans...
  
  
  
• 10 years agoHelpfull: Yes(1) No(5)
• 18x=y where in y all digits are 4
  so we can say
  9x=y where in y all digits are 2
  so,
  x=y/9
  here x is an integer so y should be divisible by 9
  and divisibility rule for 9 is sum of all digit will be divisible by 9
  and y containing only 2 so 9 digit make the sum 18 which is divisible by 9
  i.e. X*9=2222…18 times
  therefore , X= (2222….18 time)/9= 24691358
  so , no of digits in X is 8
• 7 years agoHelpfull: Yes(0) No(0)